Amos sees the Lord standing with a plumb line, and the LORD says he is setting a plumb line in the midst of Israel. The message is that he will “never again pass by them,” and it includes the downfall of high places and sanctuaries. See Amos 7:7–9.
In this vision Amos 7:7–9, Amos sees the Lord standing by a wall with a plumb line in hand. God asks Amos what he sees, and Amos answers, “a plumb line.” God then explains the sign: he is setting a measuring standard in the middle of Israel and will no longer “pass by” them, meaning the time for overlooking is over. Amos 7 begins a series of vision reports in which Amos recounts what he was shown and what it means. The first two visions (locusts and fire) include Amos pleading and God relenting; this third vision shifts from relenting to finality. The scene is structured like a simple exchange: what Amos sees becomes the message.
This vision uses a simple picture to communicate a verdict. Amos sees the Lord standing by a wall with a plumb line in hand, then hears God explain the symbol (Amos’ answer, “a plumb line,” becomes the cue for the message).
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Amos 7:7-9, then read the surrounding section so the answer stays connected to the passage's flow.
7Thus he showed me: and, behold, the Lord stood beside a wall made by a plumb-line, with a plumb-line in his hand.
8Yahweh said to me, Amos, what see you? I said, A plumb-line. Then said the Lord, Behold, I will set a plumb-line in the midst of my people Israel; I will not again pass by them any more;
9and the high places of Isaac shall be desolate, and the sanctuaries of Israel shall be laid waste; and I will rise against the house of Jeroboam with the sword.